The background verse here is this:
[Psa 118:26 NKJV] (26) Blessed [is] he who comes in the name of the LORD! We have blessed you from the house of the LORD.
The fulfillment appears here:
[Mat 21:1-11 NKJV] (1) Now when they drew near Jerusalem, and came to Bethphage, at the Mount of Olives, then Jesus sent two disciples, (2) saying to them, “Go into the village opposite you, and immediately you will find a donkey tied, and a colt with her. Loose [them] and bring [them] to Me. (3) “And if anyone says anything to you, you shall say, ‘The Lord has need of them,’ and immediately he will send them.” (4) All this was done that it might be fulfilled which was spoken by the prophet, saying: (5) “Tell the daughter of Zion, ‘Behold, your King is coming to you, Lowly, and sitting on a donkey, A colt, the foal of a donkey.’ ” (6) So the disciples went and did as Jesus commanded them. (7) They brought the donkey and the colt, laid their clothes on them, and set [Him] on them. (8) And a very great multitude spread their clothes on the road; others cut down branches from the trees and spread [them] on the road. (9) Then the multitudes who went before and those who followed cried out, saying: “Hosanna to the Son of David! ‘Blessed [is] He who comes in the name of the LORD!’ Hosanna in the highest!” (10) And when He had come into Jerusalem, all the city was moved, saying, “Who is this?” (11) So the multitudes said, “This is Jesus, the prophet from Nazareth of Galilee.”
But after this Jesus complains that they have not fulfilled it and it is still future. Why the complaint after the appropriate response?:
[Mat 23:37-39 NKJV] (37) “O Jerusalem, Jerusalem, the one who kills the prophets and stones those who are sent to her! How often I wanted to gather your children together, as a hen gathers her chicks under [her] wings, but you were not willing! (38) “See! Your house is left to you desolate; (39) “for I say to you, you shall see Me no more till you say, ‘Blessed [is] He who comes in the name of the LORD!‘ “